IMMUNE RESPONSE IN THE GUT ASSOCIATED LYMPHOID TISSUE (GALT) OF WEANED MICE AFTER INTRAGASTRIC INOCULATION OF SHIGA TOXIN (STX)-PRODUCING Escherichia coli (STEC)

FERNÁNDEZ BRANDO ROMINA J; CABRERA GABRIEL; MILIWEBSKY E; MEJIAS MP; PANEK CA; RIVAS M; PALERMO MS

Buenos Aires

Congreso; First French-Argentine Immunology Congreso. LVIII reunión anual de la Sociedad Argentina de Inmunología, XIII Jornada Científica del Grupo Rioplatense de Citometría de Flujo, 3º Jornadas Argentinas de Inmunodeficiencias Primarias (SAP); 2010

Sociedad Argentina de Inmunología (SAI), French Society of Immunology

Hemolytic Uremic Syndrome (HUS) is a life-threatening complication of STEC gastrointestinal infection and the GALT constitutes the first immune compartment encountered by STEC. We have developed a mouse model of HUS after intragastric inoculation of E.coli O157:H7 Stx+ strains (125/99) at weaning. We have previously observed a decrease of B cell percentage in Peyer’s patches (PP), with a simultaneous and  transient increase in mesenteric lymph nodes (MLN) in 125/99-inoculated mice at 24h post-inoculation compared to controls: mice inoculated with a Stx- E.coli O157:H7 strain (605/03) or PBS (Ctrl). The aim of this work was to further study the activation and trafficking of T and B lymphocytes as a related phenomenon supporting those changes. We also evaluated alterations in the CD4+CD25+ population with potential regulatory function at 7d post-inoculation. Flow cytometry analysis showed that both 125/99 and 605/03-inoculated mice presented evidence of activation as a decreased CD62L MFI in MLN (mean±SD,n) for T and B cells (B cell: Ctrl=765±39,3; 605/03=477±22,3; 125/99=518±112,3; p<0.005; T cell: Ctrl= 1764±14,3; 605/03=1156±168,3; 125/99=1195±144,3; p<0.002). Besides, an increased percentage of CD69+ B-cells was observed in MLN from both experimental groups (Ctrl=26.5±0.7,2; 605/03=35.0±4.0,3; 125/99=40.0±2.7,3; p<0.01). After 12 h of i.v. injection of allogenic CFSE+ lymphocytes only 125/99-inoculated mice showed an increased percentage of B220+CFSE+ cells in MLN (Ctrl=12.6±0.8,4; 605/03=13.1±2.7,2; 125/99=14.7±1.9,4; p<0.05). Additionally, an increased percentage of CD4+CD25+ cells was observed 7d post-inoculation only in MLN from125/99-inoculated mice (Ctrl=12.0±0.5,4; 605/03=11.7±1.9,4; 125/99=15.9±2.1,3; p<0.02). Although both E.coli strains induced GALT B and T cell activation, our results suggest that only the stimulus caused by the Stx-producing strain was able to induce trafficking of B cells and increase the CD4+CD25+ cells in the MLN.